Greg Hudson [ghudson@MIT.EDU] wrote: > On Fri, 2008-02-29 at 18:31 +0000, Alasdair G Kergon wrote: > > On Fri, Feb 29, 2008 at 12:32:41PM -0500, ghudson@MIT.EDU wrote: > > > The reproduction recipe looks like: > > > rm -rf /tmp/test > > > mkdir /tmp/test > > > # Put around 60MB of files into /tmp/test > > > find /tmp/test -type f | xargs md5sum > /tmp/sum.pre > > > lvcreate --size 2G --snapshot /dev/dink/gutsy-i386-sbuild --name testsnapshot > > > find /tmp/test -type f | xargs md5sum > /tmp/sum.post > > > > Can you do that twice? > > find /tmp/test -type f | xargs md5sum > /tmp/sum.post2 > > and check the two post files are the same? > > In three reproductions of the page cache corruption, sum.post2 was > always the same as sum.post. > > In my experiences with this problem in general, the page cache > corruption is not particularly transient; once it happens, the file > continues to appear modified (with the same incorrect contents) for the > indefinite future, until the machine is rebooted. > > > And add some syncs/blockdev --flushbufs at different places > > in the script to see if you can make it go away. > > Nope, that never made it go away. I'm not sure in what situations > flushing write buffers would have any effect. If I had a way to throw > away the read-only page cache and force a file reload from disk, I would > expect that to eliminate the visible effect of the corruption; at the > moment the only reliable way I know how to do that is to reboot. Not an expert on O_DIRECT, but it is supposed to read from the disk without creating page cache. I don't really know what it does if page cache exists! The "dd" command has O_DIRECT support and see if you notice any change with the corrupted file when you do "dd" with and without O_DIRECT. --Malahal. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
